Recent specifications have described how a personal computer (xe2x80x9cPCxe2x80x9d) should allow suspension to a power-managed sleeping state. It is desirable that the computer become available for use quicken when removed from that sleeping state. Modern specifications prefer that the PC become available within do approximately 10 seconds.
The Windows 98 current release includes support for certain kinds of power management. One is the so-called Advanced Configuration and Power Management Interface (xe2x80x9cACPIxe2x80x9d) jointly promulgated by Intel/Microsoft/Toshiba, and the xe2x80x9cOn-Nowxe2x80x9d specification published by Microsoft. These specifications describe hardware and software that facilitates placing the system into a power-managed sleep state. In the ideal case, the user would command the machine to power off, but the PC would continue to power certain components to allow a rapid restart.
Different sleep states are described in the applicable specifications. The sleep states are often called S1, S2, S3, S4, and S5. Each sleep state represents a different trade-off between power consumption and the time it takes to wake. The S3 sleep state, in which the information is suspended to RAM but certain wake-up parameters are monitored, is especially advantageous. Over 95% of the PC""s power is shut off, thereby enabling phenomenal power savings. The information is stored in DRAM, allowing the resume time to be less than 5-10 seconds. This also enables off yet communicatingxe2x80x9d capabilities in which an external stimulus, such as an incoming telephone call, will wake the system to appropriately answer the incoming call.
The S3 mode requires an auxiliary power source which powers certain system components which are called the xe2x80x9ckeep-alivexe2x80x9d logic while the system is sleeping. It is desirable that the auxiliary power supply have a capacity of 2-3 watts. This amount of power can be easily dissipated without any fans. The operation also requires a split-power plane design so that the auxiliary power source can power only those required portions. The majority of the PC, including the processor and most peripherals, remain unpowered. This allows the system to effectively resume immediately rather than booting the system each time.
In addition, the PC can wake on various external stimuli. For example, the system must be able to wake when the user wants to reuse the PC. Other system stimuli, such as incoming networkbased triggers (xe2x80x9cWake-on-Lanxe2x80x9d) should also be able to revive the sleeping PC.
This system, of course, will only work if these features work reliably. This means that the PCS must be able to successfully transition between the sleeping and waking states.
According to the present system, the operation uses a list of power managed devices, and rules for those devices. The list of devices is maintained by the operating system. The devices that are used is based on the actual hardware that is installed, as well as the system state. This list is used to determine how much power will be necessary in different system modes.
If the necessary power is beyond the power capabilities of the auxiliary power supply, then the operating system takes preventative action. A preferred prevention includes using a less aggressive sleep modexe2x80x94that is, one that consumes more main power or takes longer to wake. Another preferred prevention includes terminating power management to some of the auxiliary devices, e.g., some of the PCI cards.